MEMS ribbon arrays have proved useful in many different types of high speed light modulator. Some examples of different kinds of light modulators based on MEMS ribbon arrays are described in U.S. Pat. Nos. 7,054,051, 7,277,216, 7,286,277, and 7,940,448.
FIG. 1A is a conceptual drawing of a MEMS ribbon array 105. Ribbons, e.g. 110, 115, are mounted above a substrate 120. Application of a voltage between a ribbon and the substrate causes the ribbon to deflect toward the substrate; ribbon 110 is deflected, for example, while ribbon 115 is relaxed. Typical dimensions for a MEMS ribbon in an array are tens to hundreds of microns long, a few microns wide, and a fraction of a micron thick. Ribbons may be made from silicon nitride and coated with aluminum.
MEMS ribbons can switch between relaxed and deflected states in as little as about ten nanoseconds. The corresponding high pixel switching speed means that a linear array of MEMS ribbons can do the job of a two-dimensional light modulator. A line image produced by a linear array modulator may be swept from side to side to paint a two dimensional scene.
High-speed ribbons require high-speed electrical signals to drive them. Ribbons in a typical MEMS array need 10 to 15 volts potential difference from the substrate to deflect by a quarter optical wavelength. Switching 10 to 15 volts at hundreds of megahertz is a specialized task often requiring custom made electronic driver circuits. It would be more convenient if MEMS ribbon arrays could be driven by conventional high-speed digital electronic circuits. Tighter integration between MEMS and CMOS circuits, for example, could lead to a MEMS linear array being considered as an optical output stage for an integrated circuit.